This invention relates to a film and nonwoven fabric laminate and method for making the same.
Nonwoven fabrics typically comprise polymer fibers or filaments which are bonded or consolidated by processes other than weaving. A variety of processes are employed, including thermal bonding, chemical or adhesive bonding, ultrasonic bonding, and entanglement using barbed needles or fine water jets. Nonwoven fabrics are employed in a wide variety of applications, with the fabric often being designed to have particular properties.
Nonwoven fabrics are generally porous and have poor barrier properties to liquids. Barrier properties can be improved by treatment of the nonwoven with water repellents, such as fluorocarbon compounds. Also, it is known to laminate a barrier film onto a nonwoven fabric, either by using an adhesive between the layers, or by extrusion coating of a film onto the fabric to obtain a thermal bond. The film layer generally renders the laminate impermeable to the passage of gas, liquids and vapor.
The production of microporous and porous films is also known. A microporous film is characterized as having a pore size which is small enough to prevent transfer of liquids but large enough to permit transfer of gas and liquid vapors. The manufacture of microporous films is described in U.S. Pat. Nos. 3,745,057 and 3,870,593. The methods employed in these patents involve the hot elongation of a film of thermoplastic polymer. The elongation itself may result in pores, but preferably, the polymer will contain a pore forming material, such as a finely powdered salt, such that pores will form at particle sites when the film is stretched or elongated in the machine direction, cross machine direction, or both directions. As described in U.S. Pat. No. 4,308,303, after production of the microporous film, it may be coated with fibers using a suitable adhesive. The microporous film may also be laminated to a finished nonwoven web using conventional techniques.
There are many present and future applications for breathable nonwoven fabrics. Such fabrics have a soft, fabric-like surface on at least one side, are substantially impervious to liquids, especially water and solvents, but allow passage of liquid vapors. Present commercial uses for such fabrics include outer covers for disposable absorbent garments such as diapers, other garments, such as hospital gowns, rain wear, and other protective clothing, covers, barrier fabrics for buildings and the like.
Up to the present, the manufacture of nonwoven and microporous film laminates has required the separate fabrication of the film and the finished nonwoven, followed by subsequent lamination, with each step adding to the cost of the final product.